This game has an official coop campaign, but only lcoal couch-coop splitscreen/jointscreen. You can play this also online with as friend via Remote Play Together if you have one controller as double keyboard input is not possible this way. One advantage is only one player needs to actually buy this game.

The online party mode does more react like a sandbox. You can start levels together and do speedruns and stuff, but the story triggers works for everyone on its own. It is only good for having some quick fun.

There is an inofficial mod that can provide a real online coop campaign as far as I heard. But how good it works I don't know.